1. Field of the Invention
The present invention relates to a method for manufacturing a substrate applied in a flat panel display device, and more particularly, to a method for manufacturing a substrate for use in a thin film transistor liquid crystal display (TFT-LCD).
2. Description of Related Art
In comparison with conventional cathode ray tubes (CRTs), LCDs have advantages of low power consumption, being slim-line, and being free of radiation; however, TFT-LCDs are expensive. Especially, during photolithography for manufacturing the TFT arrays of LCDs, the quantity of masks can not effectually be decreased and this causes the final cost of the screen to be high.
In conventional technologies, six-mask or five-mask photolithography is performed to manufacture a TFT array substrate. The processes are approximately as follows. The first mask process is used for defining the first metal layer to form the components of scan lines, and the gate of TFTs etc. The second mask process is applied to define channel regions of TFTs and an ohmic contact layer. The third mask process is performed to define the second metal layer to form the components of data lines and the source/drain of TFTs etc. The fourth mask process is applied to pattern the protection layer. The fifth mask process is executed to pattern the transparent conductive layer forming pixel electrodes.
Because the conventional processes of manufacturing TFTs are time-consuming and complex, the costs are high and deficiencies, such as misalignment, production of external parasitic capacitance, and uneven etching of the channel regions etc. may easily occur. As the development in TFT-LCDs leads to products having especially large screens, the processes for manufacturing TFT substrates will face many problems, such as decrease of both the yield and the efficiency of production. Therefore, how to reduce the quantity of masks for manufacturing a TFT array substrate so as to simplify the processes thereof has become an important goal. Hence, there is a requirement for a method of manufacturing LCD substrates. The method is required to simplify the processes of photolithography to reduce the difficulty of the manufacture, besides overcoming the deficiencies, such as misalignment, production of external parasitic capacitance, and uneven etching of the channel regions etc. in the conventional processes so as to promote the yield and the efficiency of production.